Uncovering the Role of Sleep in the Acquisition of Linguistic Knowledge

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One remarkable aspect of human learning is our ability to build general knowledge from individual experiences. This general knowledge is central to virtually all cognitive functions, but is particularly important in language, as it allows us to use new words, phrases, and sentences that have not been communicated previously. For example, we understand the novel word 'untweetable' because we have general knowledge of the functions of affixes {un} and {able}. However, despite the significance of this form of knowledge for human communication, we know remarkably little about how it is acquired. Recent research provides strong clues that sleep may play a vital role in the acquisition of general linguistic knowledge. In a previous ESRC project, we developed a laboratory analogue of language learning to track how general knowledge is built through multiple experiences with individual words. This research demonstrated that although new memories for individual items can be acquired rapidly, the process of discovering regularities across individual items to permit generalisation requires a period of overnight memory consolidation. The aim of the present research project is to discover whether sleep is the critical factor in the acquisition of general linguistic knowledge, and further, to describe the neural processes arising during sleep that facilitate this form of learning. This proposal describes three work packages that combine methods at the leading edge of sleep science with our laboratory analogue of language learning to uncover how sleep impacts on the development of item-specific and general knowledge. In the first work package, we track the acquisition of item-specific and general knowledge when there is a delay between training and testing, and assess whether it matters if that delay consists of overnight sleep as opposed to daytime wake. In the second work package, we investigate how sleep deprivation before or after training impacts on the acquisition of item-specific and general linguistic knowledge. In the third work package, we use an olfactory cuing technique to reactivate memories of newly-learned information during sleep, and measure whether this reactivation enhances the acquisition of linguistic knowledge. We then take this experimental paradigm one step further to ask whether we can bias the course of long-term learning by selectively reactivating particular memories. In all experiments involving sleep, we use polysomnography to assess the importance of particular sleep stages or neural events during sleep for different forms of learning. We also assess learning in all experiments after one week to draw conclusions about the stability of new knowledge over the longer term. International research has shown that the UK has one of the largest proportions of children who are sleep deprived, and that more than a quarter of the UK population gets on average less than five hours of sleep nightly. Given these statistics, it is of vital importance to understand what the consequences of poor sleep are for learning and memory. This research programme will address profound questions about how the brain continues to process new memories during sleep, how these sleep-related neural mechanisms shape the acquisition of long-term linguistic knowledge, and how sleep prepares the brain for new learning. Our findings will be transformative for theoretical models of learning, particularly as these apply to language, and will provide a range of new opportunities for creating substantive impacts within educational settings. We have developed a full programme of engagement with academic and non-academic stakeholders to realise this potential.